1. Field of the Invention
The present invention relates to a multilayer ceramic capacitor and a method for manufacturing the same, and in particular relates to a multilayer ceramic capacitor including a multilayer body provided with a plurality of stacked dielectric layers and a plurality of internal electrodes disposed at a plurality of interfaces between the dielectric layers, and an external electrode provided on an outer surface of the multilayer body and electrically connected to some of the inner electrodes and a method for manufacturing the same.
2. Description of the Related Art
In recent years, a multilayer ceramic capacitor which is compact in size but can offer a large capacitance has been widely used in an electronic device to make the electronic device small in size and light in weight. For example, as illustrated in FIG. 2, the multilayer ceramic capacitor is configured to include a multilayer body 10 provided with a plurality of stacked dielectric layers (dielectric ceramic layers) 11 and a plurality of internal electrodes 12 disposed at a plurality of interfaces between dielectric layers 11, and a pair of external electrodes 13a and 13b disposed on both end surfaces of multilayer body 10 in conduction with internal electrodes 12 exposed alternately on opposite end surfaces.
In the multilayer ceramic capacitor mentioned above, as a material for forming the dielectric layers, a dielectric ceramic material which has a high relative dielectric constant and includes a Ba and Ti containing perovskite compound as a primary ingredient has been widely used.
As the dielectric ceramic material, a non-reducible dielectric ceramic composition is proposed (see Japanese Patent Laying-Open No. 4-169003). The non-reducible dielectric ceramic composition contains BaTiO3 at 95.0 to 98.0 mol % and rare earth oxide at 2.0 to 5.0 mol % as a principal component, and contains MnO and oxide glass mainly composed of BaO—SrO—Li2O—SiO2 as a minor component. In BaTiO3, the content of unreacted BaO is 0.7 wt % or less and a ratio of Ba/Ti is 1.005 to 1.025. The rare earth oxide contains at least one element selected from La, Nd, Sm, Dy and Er. If the principal component is set to 100 parts by weight, MnO is 0.3 to 1.5 parts by weight and the oxide glass is 0.5 to 2.5 parts by weight.
Since the non-reducible dielectric ceramic composition is superior in capacitance-temperature characteristics, when it is used as a dielectric layer (dielectric ceramic layer) in a multilayer ceramic capacitor, it is possible to make the dielectric layer thinner.
However, based on the material composition of the non-reducible dielectric ceramic composition of the prior art, when it is used as an extremely thinned dielectric layer in a multilayer ceramic capacitor, the aging variation in insulation resistance in a high temperature load test will be great, which makes it impossible to obtain a multilayer ceramic capacitor with sufficient reliability.